Bug 1791950 - Enable C++20 -Wenum-float-conversion warnings. r=firefox-build-system-reviewers,glandium

C++20 deprecates some operations involving enums and floating point types. Since these warnings are enabled by default in C++20, we won't need to manually enabled this warning after mozilla-central is compiled with -std=c++20 (bug 1768116).

https://clang.llvm.org/docs/DiagnosticsReference.html#wenum-float-conversion

Differential Revision: https://phabricator.services.mozilla.com/D160718

build/moz.configure/warnings.configure

@@ -98,6 +98,7 @@ check_and_add_warning("-Wno-range-loop-analysis")
 check_and_add_warning("-Wc++2a-compat", cxx_compiler)
 check_and_add_warning("-Wcomma-subscript", cxx_compiler)
 check_and_add_warning("-Wenum-compare-conditional")
+check_and_add_warning("-Wenum-float-conversion")
 
 # Downgrade some C++20 warnings-as-errors to warnings that we can fix after we
 # compile as C++20 (bug 1768116). They don't need to block upgrading to C++20.
@@ -105,7 +106,6 @@ check_and_add_warning("-Wno-ambiguous-reversed-operator", cxx_compiler)
 check_and_add_warning("-Wno-error=deprecated", cxx_compiler)
 check_and_add_warning("-Wno-error=deprecated-anon-enum-enum-conversion", cxx_compiler)
 check_and_add_warning("-Wno-error=deprecated-enum-enum-conversion", cxx_compiler)
-check_and_add_warning("-Wno-error=deprecated-enum-float-conversion", cxx_compiler)
 check_and_add_warning("-Wno-error=deprecated-pragma", cxx_compiler)
 check_and_add_warning("-Wno-error=deprecated-this-capture", cxx_compiler)
 check_and_add_warning("-Wno-error=deprecated-volatile", cxx_compiler)